Consider the following scenario:
You are in a Microsoft Exchange Server 2013 environment.
You have multiple domains (parent domains and child domains), and some domains are not prepared for Exchange Server 2013.
You are assigned the Full Access and Send As permissions to a shared mailbox through a security group in Outlook with auto-mapping disabled.
In this scenario, you cannot open the shared mailbox in Outlook, and you receive the following error message:
Cannot expand the folder. The set of folders cannot be opened. Microsoft exchange is not available. Either there are network problems or the exchange computer is down for maintenance.
This issue occurs because the healthy system access control list (SACL) rating that is assigned for domain controller from child domain is not prepared for Exchange Server 2013.
To resolve this issue, install Cumulative Update 7 for Exchange Server 2013.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.